1. Field of the Invention
This invention relates to cabinets and more particularly to cabinets, such as refrigerators, which are required to maintain the interior of the cabinet at a temperature differing substantially from ambient, and to methods of making such cabinets.
2. Description of the Prior Art
Many cabinet constructions, for example, those employed for household appliances and particularly for refrigerators, include an outer wall and an inner wall spaced from the outer wall, with suitable insulation being included between the outer and inner walls. Usually, the outer wall and the inner wall are made of separate components and assembled in some manner. It has been recognized that for economy of manufacture it would be desirable to fashion a refrigerator cabinet, or the major portion thereof, from a single sheet of metal which could be formed to provide both the outer wall and the inner wall. This has been particularly difficult in the case of refrigerators because the interior of the refrigerator cabinet must be maintained at a temperature differing substantially from that exterior of the cabinet. It is, therefore, necessary that some provision be made for retarding heat transfer from the outer wall to the inner wall both from the standpoint of efficiency of the refrigerator and from the standpoint of eliminating condensation of moisture on the outer wall in the region closest to the inner wall.
Various approaches have been taken in the manufacture of refrigerator cabinets with the objective of reducing cost and insuring against "sweating" of the exterior of the cabinet. In one approach, the outer wall and the inner wall or liner were formed of separate metal components and the two then supported is assembled relationship by breaker strips framing the door opening and connected to the inner and outer walls. The breaker strips were made of material having low thermal conductivity, thereby retarding heat transfer from the outer wall and eliminating sweating.
In another approach, which employed a separate metal outer wall and a separate metal inner wall or liner, the breaker strip was eliminated, and the metal liner was connected directly to the metal outer wall. Perforations were provided in a flange along the edge of the liner to retard heat transfer. To improve the appearance, these perforations were then filled with vitreous enamel. This construction still, of course, required forming the inner and outer wall in separate pieces and assembling these components by screws or other fasteners, a procedure which requires time for assembly and increases cost. Moreover, it required a specific operation to fill the perforations fully with vitreous enamel in order to insure a pleasing appearance.
Another approach has been to make the outer wall of metal and the inner wall or liner of a one-piece plastic material. This approach also requires that the outer wall and the inner wall be formed as separate parts and the two be thereafter assembled to one another.
None of these prior art constructions achieved the objective of a construction by which both the outer wall and the inner wall of the refrigerator cabinet could be formed from essentially one piece of metal, with adequate provision for retarding heat transfer and for obtaining a pleasing appearance. By this invention, the outer walls and the inner walls of a refrigerator cabinet are formed, in accordance with the method of this invention, from a single sheet of metal which, prior to being bent into assembled form, is stamped to a shape which includes appropriate notches for facilitating bending to the appropriate form and also perforations and for retarding heat transfer. Further, when assembled, the cabinet provides a pleasing appearance without the necessity of filling the perforations with any concealing material such as vitreous enamel.
Accordingly, it is an object of this invention to provide an improved refrigerator cabinet construction which facilitates manufacture and reduces cost.
It is another object of this invention to provide an improved arrangement, economical in construction, for retarding heat transfer between the outer walls and the inner liner of the refrigerator, such arrangement including provision for simply and effectively concealing perforations used to retard heat transfer.
It is a further object of this invention to provide a refrigerator cabinet construction wherein the cabinet is formed from a single sheet of metal which is stamped while in sheet form to provide the necessary shape of all parts thereof and then bent in a single operation to form the refrigerator cabinet.
It is still a further object of this invention to provide in a simple and economic manner supplementary heat at a critical region to eliminate sweating of the outer wall and door gasket, and at the same time keep the added heat load on the refrigerator system to a minimum.
It is a further object of this invention to provide an improved method for constructing a refrigerator cabinet.